Retrieving Multiple Result sets with stored procedure in php/mysqli

I have a stored procedure that has multiple result sets. How do I advance to the 2nd result set in mysqli to get those results?

Let's say it's a stored proc like:

create procedure multiples( param1 INT, param2 INT )
BEGIN

SELECT * FROM table1 WHERE id = param1;

SELECT * FROM table2 WHERE id = param2;

END $$

The PHP is something like this:

$stmt = mysqli_prepare($db, 'CALL multiples(?, ?)');

mysqli_stmt_bind_param( $stmt, 'ii', $param1, $param2 );

mysqli_stmt_execute( $stmt );

mysqli_stmt_bind_result( $stmt, $id );

Then this is the part I can't get to work. I've tried using mysqli_next_result to move to the next result set, but can't get it to work. We did get it to work with mysqli_store_result and mysqli_fetch_assoc/array/row, but for some reason all the ints get returned as blank strings.

Any one else come across this and have a solution?